In various fields of technology there is a need for correct alignment of different components and machines in relation to each other. For example, during operation of large engines, pumps and similar equipment, it is essential that an output shaft of a propelling unit, for example in the form of an engine, is correctly aligned with respect to an input shaft of a propelled unit, for example in the form of a pump. In this manner, the output power of the engine can be transferred via the rotational movement of the engine shaft to the input shaft of the pump in an optimal manner. Any misalignment of the two shafts may result in a poor efficiency and an increased risk for wear and damage to the engine or the pump.
Consequently, in the above-mentioned field of technology, there is a demand for correct alignment of the engine output shaft in relation to the input shaft of the pump. In this regard, it should be noted that the two shafts may present alignment errors of generally two different kinds. To be precise, the shafts may be disposed at a certain angle with respect to each other, which is referred to as an angular error, i.e. a “horizontal angular error” and a “vertical angular error”. Secondly, even though the shafts may be parallel to each other, they may be slightly displaced with respect to each other so that they extend along two separated directions, i.e. in a parallel manner. This is referred to as “horizontal offset” and “vertical offset”. If these errors exceed predetermined limit values, it can be assumed that the shafts, and their corresponding machines, are poorly aligned with reference to each other.
Consequently, there is a general demand for systems and methods for aligning various pieces of machinery comprising rotatable shafts. Such systems and methods may be used for engines and pumps and similar equipment. Generally, they may be used in power plants, chemical plants and oil refineries, in particular in applications which comprise high speed or in applications comprising expensive, process critical machines which are necessary to align.
According to prior art, alignment of two rotatable shafts of two machines can be carried out by means of a measuring apparatus which comprises a first measuring unit arranged for mounting on a first machine and comprising a light source for generation of light radiation in the direction towards a second measuring unit arranged for mounting on a second machine and also comprising a second light source for generation of light radiation in the direction towards the first measuring unit. Furthermore, each of the measuring units comprises a detection device for emitted light radiation. By means of this apparatus, the alignment of the two shafts of the machines can be investigated.
The above-mentioned type of measuring equipment is intended to be used when the relevant machines are standing still, i.e. when they are relatively cold and not in use for the moment.
However, it should be noted that in many applications, the alignment between an engine and a pump, for example, may change as these machines are started and operated and gradually become hot, i.e. from cold and shutdown to normal operation. For example, the alignment may vary depending on the operating temperature of the machines. The alignment may also vary depending on changes in discharge pressure (if alignment is carried out on a pump or a compressor). Also, piping strain in the shafts may cause changes in alignment between cold and hot operating conditions.
The change in alignment between a cold and a hot condition may also be influenced if the relevant machines operate in parallel, or if any changes in electrical loading or rotational forces should occur during operation.
Consequently, there are thermal factors and other parameters which affect the alignment of the machines. In particular, as explained above, a problem exists in that a correct alignment of a still-standing machine may not necessarily correspond to a correct alignment of the same machine when it is operated. This means that it will be necessary to carry out some type of adjustments in order to compensate for the fact that alignment changes will occur between a cold and a hot condition.
A previously known system for measuring the difference in alignment from a cold start condition to a hot operating condition is manufactured by the company Prüftechnik and comprises two units constituting combined transmitters and detectors to be mounted on a first, stationary machine, suitably on a bearing housing on said first machine. The transmitters comprise laser light sources. Corresponding prisms are mounted on a second, moveable machine which is intended to be adjusted so as to obtain correct alignment.
The lasers are set up, one in the vertical plane and one in the horizontal plane. The horizontal head must point toward 3 o'clock, and the vertical head must point toward 12 o'clock. After this set up, each prisms have to be aligned to reflect its corresponding laser beam into the corresponding detector. The units comprising the transmitters and detectors are connected to a control unit which transmits the data to a computer, for example of the PC type. A particular software program is used to trend the data streaming from the transmitters and detectors. This results in measuring information in the form of graphs indicating positional changes during operation of the relevant machines.
A disadvantage with this previously known system relates to the fact that it comprises four different units which must be mounted and adjusted before measurements can be carried out. This means that this system is relatively complicated and time-consuming to set up and use. In fact, the setup of this previously known system takes an experienced user about two hours per coupling to set up. This does not include the time spent by the operator programming alignment formulas into the computer. The system also requires high amounts of training to be used properly as well as extensive knowledge of computer use for an operator. It is also relatively expensive.
A further disadvantage with this previously known system relates to the fact that a separate graph is required from each alignment parameter to be monitored. This means that on a typical single coupling measurement, four different graphs are required. This results in a time-consuming operation as well as a time-consuming and complicated evaluation of the measurement data.
Another previously known system is disclosed in U.S. Pat. No. 5,077,905, which teaches a laser alignment mount assembly comprising a first measuring unit and a second measuring unit. This known assembly is adapted for alignment of two coupled shafts during a first operational condition and a second operational condition. By means of the system, an initial “zeroing” of the equipment is carried out in said first operational condition by setting a laser beam in coincidence with a target. In this manner, a zero reference is determined. When the coupled shafts are in said second operational condition, a “re-zeroing” is made by displacing one of the measuring units so as to be aligned with the target and by mechanically measuring the positional change resulting from the movement off the zero reference point when the system enters the second operational condition.
A disadvantage with the system shown in U.S. Pat. No. 5,077,905 relates to the fact that it relies on both a laser measurement system and a mechanical measurement device to gather alignment change data, i.e. for providing the result of the above-mentioned “re-zeroing”. Also, the “re-zeroing” is carried out following a mechanical manipulation of a mounting bracket.